JP2012141444A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for reliably recovering and disposing a deteriorated developer such as highly charged toner generated in a developing device.SOLUTION: An image forming apparatus includes: a latent image carrier; a developer carrier that develops latent images on the latent image carrier with a developer; developer supply means for supplying the developer to the developer carrier; developer recovery means for recovering the developer on the developer carrier and accumulating a deteriorated developer; and a latent image carrier cleaning member that removes a developer remaining on the latent image carrier from the latent image carrier. During a non-image formation period when image forming operation is not carried out, the image forming apparatus moves the deteriorated developer accumulated in the developer recovery means to the developer carrier, attaches the deteriorated developer moved to the developer carrier to the latent image carrier, and removes the deteriorated developer attached to the latent image carrier with the latent image carrier cleaning member.

Description

  The present invention relates to an image forming apparatus such as an electrophotographic printer.

In a conventional electrophotographic printer, the surface of a rotating photosensitive drum is uniformly and uniformly charged by a charging roller, and then light is applied to the surface of the charged photosensitive drum according to image information from an exposure head. An electrostatic latent image is formed, and a developing device attaches toner having a predetermined charge amount to the electrostatic latent image using electrostatic force to form a toner image, and the toner image is transferred to the transfer roller. After being transferred to the paper by the above, the image is printed on the paper by being fixed by a fixing device.
A small amount of residual toner remaining on the photosensitive drum after transfer to the paper is scraped from the photosensitive drum by a drum cleaning blade provided so as to be in sliding contact with the photosensitive drum, and is collected by a waste toner conveying spiral. The

  In the developing device at the time of image formation, unused toner replenished from the toner cartridge to the toner chamber is supplied to the developing roller by the supply roller, and between the supply roller and the developing roller and between the layer regulating blade and the developing roller. In the toner thin layer formed on the developing roller, the toner is not used for developing the electrostatic latent image. The remaining undeveloped toner is scraped off by the supply roller, temporarily collected in the toner chamber, and again supplied from the supply roller to the development roller together with the unused toner.

For this reason, when the printer is used for a long period of time, the toner may deteriorate, and a highly charged toner having a significantly increased charge amount may be generated. The highly charged toner is not exposed on the photosensitive drum from the developing device. Therefore, there is a problem that smear printing is caused and print quality is deteriorated.
In order to prevent this deterioration in print quality, in an electrophotographic printer, a set of voltages applied to the layer regulating blade during non-image formation when no image is formed, and voltages applied to the photosensitive drum, the developing roller, and the supply roller. In some cases, the combination is changed from the combination of voltages at the time of image formation, and the highly charged toner is attached to the photosensitive drum and discarded (for example, see Patent Document 1).

JP 2009-98631 A (paragraphs 0030-0035, 0123-0129, 0167, FIG. 3)

However, in the above-described conventional technology, undeveloped toner that is not used for development in the toner thin layer formed on the developing roller by the layer regulating blade is collected in the toner chamber by the supply roller. Therefore, among the highly charged toner collected in the toner chamber, it is difficult to reliably dispose of the highly charged toner existing in the toner chamber except for the vicinity of the supply roller via the developing roller on the photosensitive drum. However, there is a problem that smear printing may occur with the recent increase in the speed of printers.
SUMMARY An advantage of some aspects of the invention is to provide means for reliably collecting and discarding a deteriorated developer such as a highly charged toner generated in a developing device.

  In order to solve the above problems, the present invention provides an image forming apparatus comprising: a latent image carrier; a developer carrier that develops a latent image on the latent image carrier with a developer; and the developer carrier. Developer supplying means for supplying the developer; developer collecting means for collecting the developer on the developer carrying member and accumulating the deteriorated developer; and the developer remaining on the latent image carrying member. A latent image carrier cleaning member that removes the latent image carrier from the latent image carrier, and when the non-image forming operation is not performed, the deteriorated developer accumulated in the developer collecting means is stored in the developer carrier. The deteriorated developer moved and moved to the developer carrier is attached to the latent image carrier, and the deteriorated developer attached to the latent image carrier is removed by the latent image carrier cleaning member. It is characterized by doing.

  As a result, according to the present invention, the deteriorated developer generated in the developing device can be reliably collected by the developer collecting means and automatically discarded at the time of non-image formation, thereby preventing the occurrence of smudge printing in high-speed printing. Thus, the effect that the printing quality can be improved is obtained.

Explanatory drawing which shows the cross section of schematic structure of the image formation part of Example 1. FIG. Explanatory drawing which shows the cross section of the printing mechanism of Example 1. Explanatory drawing which shows the cross section of the collection | recovery roller of Example 1. 1 is a block diagram illustrating a printer control system according to a first embodiment. Explanatory drawing which shows the voltage of each part at the time of image formation of Example 1 and non-image formation Time chart showing timing of control operation of embodiment 1 Explanatory drawing which shows the evaluation result of the evaluation test of Example 1 Explanatory drawing which shows the voltage of each part at the time of image formation of Example 2, and the time of non-image formation Time chart showing timing of control operation of embodiment 2 Explanatory drawing which shows the evaluation result of the evaluation test of Example 2

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.

In the following description, the printer as the image forming apparatus will be described as a non-magnetic one-component electrophotographic color printer.
In FIG. 1, reference numeral 1 denotes an image forming unit of a printer, which forms a color image by superimposing a toner image as a developer image with toner as a developer of four colors on a sheet 2 as a printing medium, The color image is transferred and fixed on the paper 2 to form an image on the paper 2.

  The image forming unit 1 according to the present exemplary embodiment includes four printing mechanisms 4k, 4y, 4m, and 4c that form images of respective colors including black (K), yellow (Y), magenta (M), and cyan (C). Since each printing mechanism 4 has the same structure, only one printing mechanism 4 will be described below.

As shown in FIG. 2, the printing mechanism 4 includes a photosensitive drum 5 and a charging roller 6, an exposure head 7, a developing device 8, a transfer roller 9, a drum cleaning blade 10, a static eliminating device 11, and the like disposed around the photosensitive drum 5. It has.
The developing device 8 includes a developing roller 13, a supply roller 14, a layer regulating blade 15, a collection roller 16, a toner cartridge 17, a toner chamber 18, and the like.

The photosensitive drum 5 as a latent image carrier is a cylindrical member in which a photoconductive layer is formed on the outer peripheral surface of a drum-shaped conductor such as aluminum, and an electrostatic latent image and the electrostatic latent image are formed on the photoconductive layer. A toner image obtained by developing the toner with toner is formed.
Further, a gear (not shown) for obtaining a rotational driving force from the drive motor 5a is provided at one end of the photosensitive drum 5, and is referred to as a paper 2 transport direction (paper transport direction A) indicated by an arrow A in FIG. ) Is driven so as to rotate in the rotation direction in which the sheet 2 is conveyed (clockwise in FIG. 2 and referred to as the conveyance rotation direction).

A charging roller 6 as a charging unit contacts the photosensitive drum 5 and rotates in a direction opposite to the photosensitive drum 5 (counterclockwise in FIG. 2), and a charging voltage power source 6b (voltage applying unit of the charging roller 6) ( The surface of the photosensitive drum 5 is uniformly and uniformly charged with the charging voltage Vch applied from FIG.
An exposure head 7 serving as an exposure unit is disposed above the photosensitive drum 5 so as to be opposed to each other, and includes a plurality of LEDs (Light Emitting Diodes) serving as light emitting elements, and exposes the surface of the photosensitive drum 5 based on image information. Thus, an electrostatic latent image is formed.

  The developing roller 13 as a developer carrying member is a cylindrical member having a conductive material such as stainless steel as a shaft, and an outer peripheral surface of the shaft covered with an elastic material of urethane rubber having a rubber hardness of 70 (Asker C). A developing voltage power source which is a voltage applying means of the developing roller 13 is rotated at a peripheral speed faster than the peripheral speed of the photosensitive drum 5 in contact with the photosensitive drum 5 and in a direction opposite to the photosensitive drum 5 (counterclockwise in FIG. 2). A toner image is formed by attaching toner to the electrostatic latent image on the photosensitive drum 5 by the developing voltage Vdv applied from 13b.

  The supply roller 14 as the developer supply means is a cylindrical member having a conductive material such as stainless steel as a shaft, and an outer peripheral surface of the shaft coated with a silicone foaming elastic material having a rubber hardness of 50 (Asker F). The surface of the developing roller 13 contacts the surface of the developing roller 13 and rotates in the same direction as the developing roller 13 (counterclockwise in FIG. 2). Toner supplied to a toner chamber 18 as a developer chamber from a toner cartridge 17 as a developer container is supplied to the developing roller 13.

  The layer regulating blade 15 as a developer layer regulating member is a plate-like member made of stainless steel having a thickness of 0.1 mm which is a metal having elasticity, and one end thereof is developed as shown in FIG. It is fixed to the frame of the apparatus 8, the other free end is brought into contact with the developing roller 13, and is provided between the supply roller 14 and the photosensitive drum 5 on the downstream side in the rotation direction of the developing roller 13. The layer regulation voltage Vbl is applied from a layer regulation voltage power source 15b which is a voltage application unit of the layer regulation blade 15.

  As shown in FIG. 3, the collecting roller 16 as a developer collecting unit uses a conductive material such as stainless steel as a collecting roller shaft 20, and a foam layer 21 made of a silicone foam is formed on the outer peripheral surface of the collecting roller shaft 20. A cylindrical member provided with a mesh layer 22 that is coated and formed by winding a mesh member having an opening of 10 μm on the outer peripheral surface of the foam layer 21, and the rotational direction of the developing roller 13 of the photosensitive drum 5 2 is arranged in contact with the surface of the developing roller 13 in the toner chamber 18 between the supply roller 14 (see FIG. 2) and is driven to rotate by the driving motor 16a to form the developing roller 13 during image formation. In the toner thin layer formed by the layer regulating blade 15 on the developing roller 13 that rotates in the same direction (arrow B direction shown in FIG. Photosensitivity And scrape the undeveloped toner as remaining undeveloped developer not used for development of an electrostatic latent image on the drum 5 is recovered into the toner chamber 18.

Further, the recovery roller 16 deteriorates and develops a highly charged toner, a small particle size toner, or the like by a recovery voltage Vre applied to the recovery roller shaft 20 from a recovery voltage power supply 16b that is a voltage application unit of the recovery roller 16 during image formation. It has a function of accumulating deteriorated toner as an agent in the foam layer 21. The accumulation effect of the deteriorated toner on the foam layer 21 will be described later.
Further, the collecting roller 16 rotates at the same peripheral speed as the developing roller 13 in the reverse direction to the forward rotation direction B (referred to as the reverse rotation direction C) during non-image formation when no image forming operation is performed. 2 has a function of moving the deteriorated toner accumulated in the developing roller 13 to the developing roller 13.

  As shown in FIG. 2, the transfer roller 9 serving as a transfer unit is disposed opposite to the photoconductive drum 5 with the conveyance belt 23 that contacts the photoconductive drum 5 and conveys the paper 2 interposed therebetween. The toner image formed on the photosensitive drum 5 is transferred onto the paper 2 transported by the transport belt 23 by the transfer voltage Vtr applied from the transfer voltage power supply 9b as a means.

  The drum cleaning blade 10 as a latent image carrier cleaning member is disposed on the downstream side of the transfer roller 9 in the conveyance rotation direction of the photosensitive drum 5 with the tip thereof being in sliding contact with the surface of the photosensitive drum 5. The toner remaining on the surface of the photosensitive drum 5 after the transfer of the toner image to the paper 2 is scraped off and removed.

The toner removed from the photosensitive drum 5 by the drum cleaning blade 10 is once stored in a waste toner transport path 24 which is a space for transporting the toner, and a waste toner storage chamber (not shown) by a waste toner transport spiral 25. Is housed in.
A waste toner transport spiral 25 as a waste developer transport means is a shaft-like member having a spiral groove formed on the outer peripheral surface thereof, and rotates in synchronization with the rotation of a gear (not shown) of the photosensitive drum 5 so as to waste toner. The toner once stored in the transport path 24 is transported to a waste toner storage chamber (not shown) by rotation of the spiral groove.

  The neutralization device 11 as a neutralization unit is a device using, as a light source, an LED disposed opposite to the photosensitive drum 5 between the drum cleaning blade 10 and the charging roller 6 on the downstream side in the conveyance rotation direction of the photosensitive drum 5. Thus, it has a function of initializing the charging potential of the photosensitive drum 5.

  As shown in FIG. 1, the conveyance belt 23 as a medium conveyance means is an endless belt that is stretched between a drive roller 27 and a driven roller 28 that are rotationally driven by a drive motor 27 a. A belt cleaning blade 29 as a medium conveying means cleaning member for scraping off toner remaining on the surface of the conveying belt 23 is provided on the surface of the conveying belt 23 in the vicinity of the driven roller 28 on the downstream side in the rotation direction. The toner removed by the belt cleaning blade 29 is accommodated in the waste toner tank 30 so as to be in sliding contact.

  A fixing device 31 is disposed on the downstream side of the conveyance belt 23 in the sheet conveyance direction A, and is a heating roller 32 that is rotationally driven by a drive motor 32a and a pressure roller that is disposed opposite to the sheet while conveying the sheet 2 conveyance path. 33 and the like are provided, and the toner image transferred to the paper 2 is melted by heating and pressing to fix the toner image on the paper 2.

  The toner used in this example includes polyester as a binder resin, carbon black as a colorant, copper phthalocyanine pigment (CI Pigment Blue 15), quinacridone pigment (CI Pigment Red 122), C.I. I. Negatively chargeable pulverized toner using Pigment Yellow 185 or the like, and its volume average particle diameter is 5.5 μm, and additives such as silica having various charging characteristics are externally added to adjust fluidity and chargeability. Is formed. “CI” indicates the name of a dye or pigment registered with the British Dye Staining Society (SDC).

  In FIG. 4, reference numeral 35 denotes a printer control unit which drives the drive motor 5a for driving the photosensitive drum 5, the drive motor 27a for driving the drive roller 27, the drive motor 32a for driving the heating roller 32, and the collection roller 16. Drive motor 16a, charging voltage power supply 6b for applying charging voltage Vch to charging roller 6, development voltage power supply 13b for applying developing voltage Vdv to developing roller 13, supply voltage power supply 14b for applying supply voltage Vsp to supply roller 14, and layers A layer regulation voltage power source 15b that applies a layer regulation voltage Vbl to the regulation blade 15, a recovery voltage power source 16b that applies a recovery voltage Vre to the recovery roller shaft 20, a transfer voltage power source 9b that applies a transfer voltage Vtr to the transfer roller 9, and exposure During non-image formation when the head 7 or the like is controlled to perform print processing during image formation or no image formation operation To execute the definitive deterioration toner disposal processing, or the like.

A storage unit 36 of the printer is a read-only ROM that stores a program having a function of performing a printing process and a deteriorated toner disposal process executed by the control unit 35, various data used for the processing, a control unit, and the like. RAM etc. which store the processing result by 35, etc. are provided.
In the ROM of the storage unit 36, a charging voltage table 37 in which a charging voltage Vch0, a developing voltage Vdv0, a supply voltage Vsp0, a layer regulation voltage Vbl0, a recovery voltage Vre0, and a transfer voltage Vtr0 are set, and deterioration is performed. A deteriorated toner discard voltage table 38 in which the charging voltage Vch1, the developing voltage Vdv1, the supply voltage Vsp1, the layer regulation voltage Vbl1, the recovery voltage Vre1, and the transfer voltage Vtr1 are set is stored in advance (the value of each voltage). (See FIG. 5).

The printing operation of each unit during the printing process (image formation) of the printer of this embodiment will be described below with reference to FIGS.
When a printing command is received from a host device such as a personal computer (not shown), the printer control unit 35 starts a printing process according to the printing command (time t1 shown in FIG. 6), and transmits a driving command to each drive motor. Rotate each part.

  That is, the control unit 35 moves the photosensitive drum 5, the charging roller 6, the developing roller 13, and the supply roller 14 in the direction of the arrow shown in FIG. 2 by the driving motor 5a, and the driving roller 27 and the heating roller by the driving motor 27a and the driving motor 32a. The roller 32 is rotated in the direction of the arrow shown in FIG. 1, and the collection roller 16 is rotated at a predetermined peripheral speed in the normal rotation direction B, that is, in the same direction as the developing roller 13 by the drive motor 16a.

  At the same time, the control unit 35 reads the applied voltage to each unit during printing from the printing voltage table 37 stored in the storage unit 36 and synchronizes with the start of rotation driving by the charging voltage power source 6b to charge the charging roller. 6, the developing voltage Vch0 is applied to the developing roller 13 by the developing voltage power supply 13b, the supply voltage Vsp0 is supplied to the supplying roller 14 by the supply voltage power supply 14b, and the layer regulating voltage Vbl0 is applied to the layer regulating blade 15 by the layer regulating voltage power supply 15b. The recovery voltage Vre0 is applied to the recovery roller shaft 20 by the recovery voltage power supply 16b, and the transfer voltage Vtr0 is applied to the transfer roller 9 by the transfer voltage power supply 9b.

  In the printing operation of this embodiment, the polarities of the charging voltage Vch0, the photosensitive drum potential Vdr0, the developing voltage Vdv0, the supply voltage Vsp0, the layer regulation voltage Vbl0, and the recovery voltage Vre0 are the same as the charging polarity of the toner. The charging voltage Vch0 is set to -1000V, the developing voltage Vdv0 is set to -200V, the supply voltage Vsp0 is set to -300V, the layer regulation voltage Vbl0 is set to -300V, the recovery voltage Vre0 is set to -100V, and the transfer voltage Vtr0 is set to + 3000V (see FIG. 5). ).

By applying the charging voltage Vch0 to the charging roller 6 during printing, the surface of the photosensitive drum 5 is uniformly and uniformly charged to the photosensitive drum potential Vdr0 (−500 V) during printing (see FIG. 5).
Then, the control unit 35 causes the exposure head 7 to emit light in accordance with image information (page signal, image data, etc.) based on the print command, irradiates the photosensitive drum 5 with the light, and then onto the photosensitive drum 5. An electrostatic latent image is formed by setting the surface potential of the exposed portion to a latent image voltage Vdre.

  At this time, the toner stored in the toner chamber 18 of the developing device 8 is supplied to the supply roller 14 by the rotation of the supply roller 14 in the same direction as the development roller 13 and the electric field formed by the development voltage Vdv0 and the supply voltage Vsp0. The toner supplied to the developing roller 13 by electrostatic force directed from the developing roller 13 to the developing roller 13 is conveyed by the rotation of the developing roller 13 in the direction opposite to the conveying rotation direction of the photosensitive drum 5, and the developing roller 13 A thin toner layer having a uniform thickness is formed on the developing roller 13 by the layer regulating blade 15 disposed in contact with the downstream side of the rotational direction 13. When the toner thin layer is formed, the charge amount of the toner in the toner thin layer becomes a predetermined value by the layer regulation voltage Vbl0.

  The toner that has passed through the layer regulating blade 15 is further conveyed in the direction of the photosensitive drum 5 by the rotation of the developing roller 13 and is generated by the latent image voltage Vdre of the photosensitive drum 5 and the developing voltage Vdv0 of the developing roller 13. The toner on the developing roller 13 adheres to the electrostatic latent image formed according to the image data on the photosensitive drum 5 by the electrostatic force of the force lines, and a toner image is developed by developing the electrostatic latent image. .

  On the other hand, when the sheet 2 is conveyed in the sheet conveying direction A by the rotation of the driving roller 27 and the driven roller 28 of the conveying belt 23 in the arrow direction shown in FIG. The toner image formed on the photosensitive drum 5 is transferred onto the sheet 2 by the transfer voltage Vtr0 applied to the transfer roller 9 provided, and then the sheet 2 is further transferred to the fixing device 31 by the transport belt 23. In the fixing device 31, the toner is melted by the heating roller 32 and the pressure roller 33 to fix the toner image on the paper 2. The paper 2 on which the toner image is fixed is discharged to the outside of the printer.

  Then, the light emission operation of the exposure head 7 corresponding to the page of the received print command is completed, a corresponding toner image is formed on the photosensitive drum 5, and the toner image on the photosensitive drum 5 is transferred to the paper 2. When the toner image on the sheet 2 is fixed by the fixing device 31 and the sheet 2 of the last page is discharged from the printer, the printing process is completed, and the printing process time is L0 (see FIG. 6).

  When the toner image is transferred onto the paper 2, some toner may remain on the photoreceptor drum 5 after the transfer. This remaining toner is downstream in the conveyance rotation direction of the photoreceptor drum 5. The removed toner is removed by the drum cleaning blade 10 disposed on the side, and the removed toner is transported and stored in a waste toner transport path 24 toward a toner storage chamber (not shown) by rotation of the waste toner transport spiral 25.

Further, when the surface of the photosensitive drum 5 that has passed the drum cleaning blade 10 passes through the static eliminator 11 disposed on the downstream side in the conveyance rotation direction of the photosensitive drum 5, the photosensitive drum 5 is irradiated with light from the static eliminator 11. Residual charges such as unexposed charges above are removed, and the charged potential of the photosensitive drum 5 is initialized. Thus, the photosensitive drum 5 is repeatedly used.
Further, the toner remaining on the conveyance belt 23 is removed by a belt cleaning blade 29 disposed in sliding contact with the conveyance belt 23 on the downstream side in the rotation direction of the conveyance belt 23, and the removed toner is disposed in the waste toner tank 30. Be contained. Thus, the conveyor belt 23 is used repeatedly.

  Further, the undeveloped toner that remains on the developing roller 13 and is not used for developing the electrostatic latent image on the photosensitive drum 5 from the contact portion between the developing roller 13 and the photosensitive drum 5. Also, the collecting roller 18 disposed downstream in the rotation direction of the developing roller 13 is scraped off by the rotation in the normal rotation direction B, that is, the rotation in the same direction as the developing roller 13, and is collected in the toner chamber 18.

  The undeveloped toner includes toner deteriorated by rubbing between the supply roller 14 and the developing roller 13, the layer regulating blade 15 and the developing roller 13, and the photosensitive drum 5 and the developing roller 13. There is a case. The term “deterioration” as used herein means that the toner is reduced in particle size due to abrasion due to rubbing, or the additive is charged to a higher potential than normal toner due to peeling off due to rubbing.

When such a small particle size toner enters a gap between normal large particle size toners, the density of the toner thin layer increases, resulting in a high surface potential of the toner thin layer, which causes smear printing.
Further, since the potential of the highly charged toner becomes higher than the photosensitive drum potential Vdr0, it easily adheres to the non-exposed portion and causes smear printing as in the case of the small particle size toner.

  In this embodiment, the deteriorated toner such as the small particle size toner and the highly charged toner is selectively collected from the undeveloped toner by the collecting roller 16 and accumulated in the foam layer 21 of the collecting roller 16, so that the undeveloped toner is collected. The deteriorated toner is removed from the toner so that the deteriorated toner does not enter the toner chamber 18.

  That is, in this embodiment, the development voltage Vdv0 (−200 V in this embodiment) is applied to the developing roller 13 and the recovery voltage Vre0 (−100 V in this embodiment) is applied to the recovery roller shaft 20 of the recovery roller 16. The toner on the developing roller 13 receives an electrostatic force toward the collecting roller 16 due to the electric field formed by the voltage difference.

  Among them, the small particle size toner passes through the mesh layer 22 by the rubbing between the mesh layer 22 and the developing roller 13 in the collecting roller 16 and is stored in the foam layer 21. Further, the highly charged toner is electrostatically strong enough to be able to pass through the mesh layer 22 from the developing roller 13 toward the collecting roller shaft 20 by the electric field formed between the developing roller 13 and the collecting roller shaft 20 in the collecting roller 16. In order to receive the force, it passes through the mesh layer 22 and is stored in the foam layer 21.

Thus, since the collection roller 16 of this embodiment is provided with the mesh layer 22 and the foam layer 21, the small particle size toner and the highly charged toner are selectively collected and accumulated in the collection roller 16. can do.
The undeveloped toner from which the deteriorated toner has been removed is returned to the toner chamber 18 and is supplied to the developing roller 13 together with the unused toner by the rotation of the supply roller 14 and is used again for developing the electrostatic latent image. Thus, the developing roller 13 is used repeatedly.
As described above, the printing process by the printer of this embodiment is executed.
Next, the discarding operation of the deteriorated toner discarding process of the printer of this embodiment will be described.

  The deteriorated toner discarding step for discarding the deteriorated toner described below is performed during a non-printing operation (non-image forming) other than the printing operation (image forming operation) described above. Further, discarding the deteriorated toner means that at least the deteriorated toner is discharged from the developing device 8 to the outside.

  In the deteriorated toner disposal process of this embodiment, the photosensitive drum 5, the charging roller 6, the developing roller 13, and the supply roller 14 are moved in the direction of the arrow shown in FIG. 2 by the drive motor 5a, and the drive roller 27 is driven by the drive motor 27a. 1 and the collection roller 16 is rotated by the drive motor 16a in the reverse rotation direction C, that is, in the reverse direction to the developing roller 13 at the same peripheral speed. Note that the fixing device 31 shifts to a standby state.

  Further, as the applied voltage to each unit, each applied voltage recorded in the deteriorated toner discarding voltage table 38 stored in the storage unit 36 is used, and the charging voltage Vch1 is applied to the charging roller 6 by the charging voltage power source 6b. The developing roller 13 collects the developing voltage Vdv1 by the developing voltage power supply 13b, the supply roller 14 collects the supply voltage Vsp1 by the supply voltage power supply 14b, and the layer regulating blade 15 collects the layer regulating voltage Vbl1 by the layer regulating voltage power supply 15b. A recovery voltage Vre1 is applied to the roller shaft 20 by a recovery voltage power supply 16b, and a transfer voltage Vtr1 is applied to the transfer roller 9 by a transfer voltage power supply 9b.

  The charging voltage Vch1, the photosensitive drum potential Vdr1, the development voltage Vdv1, the supply voltage Vsp1, the layer regulation voltage Vbl1, and the recovery voltage Vre1 are the same as the charging polarity of the toner during the degraded toner discarding operation of this embodiment. The charging voltage Vch1 is set to 0V, the developing voltage Vdv1 is set to -200V, the supply voltage Vsp1 is set to -200V, the layer regulation voltage Vbl1 is set to -300V, the recovery voltage Vre1 is set to -1000V, and the transfer voltage Vtr1 is set to 0V (FIG. 5). The charge potential Vch1 = 0V of the charging roller 6 when the deteriorated toner is discarded causes the surface potential Vdr1 = 0V of the surface of the photosensitive drum 5 (see FIG. 5).

When discarding the deteriorated toner in this embodiment, as described above, the absolute value of the supply voltage Vsp1 is made the same as the absolute value of the development voltage Vdv1, and the absolute value of the recovery voltage Vre1 is made larger than the absolute value of the development voltage Vdv1. The voltage difference is + 800V. The layer regulation voltage Vbl1 is −300 V, which is the same as that during the printing operation, and the transfer voltage Vtr1 is 0 V without being applied.
The reason why the absolute value of the collection voltage Vre1 is made larger than the absolute value of the development voltage Vdv1 is to move the deteriorated toner accumulated in the collection roller 16 to the developing roller 13 side.

  The absolute value of the supply voltage Vsp1 and the absolute value of the development voltage Vdv1 are the same because the normal toner such as unused toner in the toner chamber 18 or normally charged undeveloped toner is supplied with the supply voltage Vsp1 and the development voltage Vdv1. This is to prevent the electrostatic force received from the electric field formed by and from contributing to the formation of the toner thin layer on the developing roller 13. Further, since the deteriorated toner has already adhered on the surface of the developing roller 13 as will be described later, the possibility that normal toner is transported with the rotation of the developing roller 13 is reduced. Since the normal toner adheres to the deteriorated toner, it is scraped off by the layer regulating blade 15 and cannot pass through the layer regulating blade 15.

  In the deteriorated toner discarding process of the present embodiment, the control unit 35 finishes printing a predetermined number of sheets (1000 sheets in the present embodiment, which will be described later) in the above-described printing process (time shown in FIG. 6). t2) The applied voltage to each part at the time of discarding the deteriorated toner is read from the deteriorated toner discard voltage table 38 stored in the storage unit 36, and the charging voltage Vch1 is applied to the charging roller 6 by the charging voltage power supply 6b. The developing voltage Vdv1 is applied to the developing roller 13 by 13b, the supply voltage Vsp1 to the supply roller 14 by the supply voltage power supply 14b, the layer regulating voltage Vbl1 to the layer regulating blade 15 by the layer regulating voltage power supply 15b, and the collecting roller shaft by the collecting voltage power supply 16b. A recovery voltage Vre1 is applied to 20 and a transfer voltage Vtr of the transfer roller 9 is transferred by a transfer voltage power source 9b. = Applying a 0V (power OFF).

  In addition, the controller 35 reversely rotates the direction of the current flowing through the drive motor 16a in the state where the drive motors 5a and 27a continue to rotate at time t2, that is, in the reverse direction to the developing roller 13. Switch to the direction of rotation.

  Thus, the photosensitive drum 5, the developing roller 13, and the supply roller 14 are in the direction of the arrow in FIG. 2, the driving roller 27 is in the direction of the arrow in FIG. 1, and the collecting roller 16 is rotated in the reverse direction C. The deteriorated toner accumulated in the foam layer 21 of the collecting roller 16 is rotated with the collecting roller shaft 20 and developed at the contact portion thereof as the collecting roller 16 rotates. Due to the voltage difference with the roller 13, the toner moves from the collecting roller 16 to the developing roller 13 due to the electrostatic force, and the collecting roller 16 and the developing roller 13 do not rub against each other. Move to.

  With the rotation of the collecting roller 16, the time when the deteriorated toner for one round has been transferred to the developing roller 13 is time t3. At this time t3, the collecting voltage Vre is switched to the collecting voltage Vre0 during printing. At time t4, the control unit 35 causes all the light emitting elements of the exposure head 7 to emit light to start exposure of the photosensitive drum 5, and forms an electrostatic latent image on the surface over the entire length of the photosensitive drum 5. The exposure ends at t5.

  On the other hand, the deteriorated toner that has moved to the developing roller 13 passes through the layer regulating blade 15 as the developing roller 13 rotates, and the deteriorated toner that has passed through the layer regulating blade 15 is further conveyed by the rotation of the developing roller 13. At time t6, when the leading edge of the deteriorated toner for one rotation of the collection roller 16 reaches the contact portion between the developing roller 13 and the photosensitive drum 5, the latent image voltage Vdre of the photosensitive drum 5 and the developing roller 13 The deteriorated toner moves from the developing roller 13 to the photosensitive drum 5 due to the electrostatic force of the electric lines of force generated by the developing voltage Vdv1, and at time t7, the deteriorated toner for one round of the collection roller 16 is transferred to the photosensitive drum 5. Finish moving to.

The deteriorated toner that has moved onto the photosensitive drum 5 is conveyed along with the rotation of the photosensitive drum 5 and is scraped off from the photosensitive drum 5 by the drum cleaning blade 10. Finish the removal of the deteriorated toner.
The time from the time t2 until the deteriorated toner for one rotation of the collection roller 16 is scraped off by the drum cleaning blade 10 is the deteriorated toner discarding process time L1 of this embodiment.

The deteriorated toner removed from the photosensitive drum 5 by the drum cleaning blade 10 is transported through the waste toner transport path 24 by the waste toner transport spiral 25 and stored in a toner storage unit (not shown) within the next printing process time L0. .
As described above, the deteriorated toner discarding process is executed by the printer of this embodiment.

  In order to confirm the effect of the waste toner disposal processing of this example, the following evaluation test was performed.

In the evaluation test, when continuous printing of 0.3% duty was performed on A4 size paper at a printing speed of 42 pages / minute, if the deteriorated toner discarding process of this embodiment is performed every time printing is performed, dirty printing is performed. Was tested and compared with the printer of Patent Document 1 (referred to as the prior art). The evaluation results are shown in FIG.
Note that 0.3% duty is 100% duty when the entire surface of the photosensitive drum 5 is exposed by the exposure head 7 and printed on the entire printable area. It means a state where printing is performed by exposing the photosensitive drum 5 corresponding to an area of 0.3%.

The reason why the print duty of the evaluation test was set to 0.3% was to confirm that the toner thin layer was normally formed on the developing roller 13 in the printed portion and to remove most of the toner thin layer on the developing roller 13. This is to increase the chance of generation of deteriorated toner as undeveloped toner.
As shown in FIG. 7, in the prior art, when printing is performed at a printing speed of 42 pages / minute, smudge printing occurs. In this embodiment, however, the deteriorated toner is discarded once every 1000 sheets of A4 size paper printed. By performing the process, good print quality with no stain was obtained even at a printing speed of 42 pages / minute.

  In the above evaluation test, if the deteriorated toner discarding process is performed at the end of the printing process, the toner consumption increases more than necessary, and the waste toner transport path 24 may be clogged with toner. In this embodiment, the predetermined number of sheets for executing the toner discarding process is set for every 1000 sheets of printing.

As described above, in this embodiment, deteriorated toner such as highly charged toner and small particle size toner having a significantly increased charge amount is temporarily accumulated in the collecting roller 16 in the printing process, and the accumulated deteriorated toner is In the process of discarding deteriorated toner during image formation, the toner is moved from the collection roller 16 to the photosensitive drum 5 via the developing roller 13, and the deteriorated toner moved onto the photosensitive drum 5 is removed by the drum cleaning blade 10 and discarded. As a result, it is possible to suppress a reduction in the accumulation efficiency of the deteriorated toner of the collecting roller 16, and as a result, it is possible to prevent the occurrence of printing defects such as smudge printing and to always obtain an output image with good print quality.
Further, in the deteriorated toner discarding process of this embodiment, the voltage applied to the supply roller 14 and the developing roller 13 is set to be the same, so that normal toner is prevented from being supplied from the supply roller 14 to the developing roller 13. can do.

  As described above, in this embodiment, the developing device of the printer is provided with a collecting roller that collects undeveloped toner on the developing roller and accumulates deteriorated toner, and collects it during non-image formation when no image forming operation is performed. The deteriorated toner accumulated on the roller is moved to the developing roller, the deteriorated toner moved to the developing roller is attached to the photosensitive drum, and the deteriorated toner attached to the photosensitive drum is removed by the drum cleaning blade. As a result, the deteriorated toner generated in the developing device can be reliably collected by the collecting roller and automatically discarded when non-image is formed, preventing the occurrence of smudge printing in high-speed printing and improving the print quality. Can be made.

  Hereinafter, the printer of this embodiment will be described with reference to FIGS. In addition, the same part as the said Example 1 attaches | subjects the same code | symbol, and abbreviate | omits the description.

  In the ROM of the storage unit 36 of the present embodiment, a printing voltage table 37 in which applied voltages at the time of the printing processing of the respective sections as in the first embodiment are set, the charging voltage Vch1 at the time of disposal of the deteriorated toner, and the development voltage. A deteriorated toner disposal voltage table 38 in which Vdv1, supply voltage Vsp1, layer regulation voltage Vbl1, and recovery voltage Vre1 are set to the same applied voltages as in the first embodiment, and the transfer voltage Vtr1 at the time of disposal of deteriorated toner is set to + 3000V. Stored in advance (see FIG. 8 for values of each voltage).

Since the printing operation of each part during the printing process (image formation) of the printer of the present embodiment is the same as that of the first embodiment, the description thereof is omitted.
The discarding operation of the deteriorated toner discarding process of the printer of this embodiment will be described below with reference to FIGS. The deteriorated toner discarding process of this embodiment is performed during a non-printing operation (non-image forming) other than the printing operation (image forming operation), as in the first embodiment.

  In the deteriorated toner discarding process, when the control unit 35 finishes printing a predetermined number of sheets (1000 sheets in this embodiment) in the printing process (time t2 shown in FIG. 9), the deteriorated toner stored in the storage unit 36 is discarded. The voltage applied to each part when the deteriorated toner is discarded is read from the hourly voltage table 38, the charging voltage Vch1 is applied to the charging roller 6 by the charging voltage power supply 6b, the developing voltage Vdv1 is applied to the developing roller 13 by the developing voltage power supply 13b, and the supply voltage power supply 14b. The supply voltage Vsp1 is applied to the supply roller 14, the layer regulation voltage Vbl1 is applied to the layer regulation blade 15 by the layer regulation voltage power supply 15b, the collection voltage Vre1 is applied to the collection roller shaft 20 by the collection voltage power supply 16b, and transferred by the transfer voltage power supply 9b. As the transfer voltage Vtr1 of the roller 9, + 3000V is applied.

Further, the control unit 35 continues the rotation of the drive motor 5a at the time t2, and reverses the direction of the current flowing through the drive motor 16a, that is, the reverse rotation C, that is, the rotation direction reverse to the developing roller 13. Switch to.
The subsequent operation of each part and the movement of the deteriorated toner up to time t7 are the same as those in the first embodiment, and a description thereof will be omitted.

The deteriorated toner moved onto the photosensitive drum 5 is conveyed as the photosensitive drum 5 rotates, and the toner conveyed to the contact portion between the photosensitive drum 5 and the conveying belt 23 is transferred to the photosensitive drum 5 and the transfer roller 9. Due to the voltage difference, the toner is transferred from the photosensitive drum 5 onto the conveyor belt 23 and moved, and at time t8a, the deteriorated toner for one rotation of the collection roller 16 finishes moving on the conveyor belt 23.
The time from the above-described time t2 until the deteriorated toner for one rotation of the collection roller 16 finishes moving on the conveying belt 23 is the deteriorated toner discarding process time L1a of this embodiment.

  The deteriorated toner that has moved from the photosensitive drum 5 onto the conveyance belt 23 is conveyed to the belt cleaning blade 29 as the conveyance belt 23 rotates within the next printing process time L0, and is scraped off by the belt cleaning blade 29. The removed deteriorated toner is stored in the waste toner tank 30.

Note that the toner remaining on the photosensitive drum 5 after the transfer to the conveyor belt 29 is removed by the drum cleaning blade 10 in the same manner as in the first embodiment, and the removed toner is removed within the next printing process time L0. The waste toner transport spiral 25 transports the waste toner transport path 24 to a toner storage chamber (not shown).
In this way, the deteriorated toner discarding process is executed by the printer of this embodiment.

  As described above, in this embodiment, in the deteriorated toner discarding process, the transfer voltage Vtr1 = + 3000 V is applied to the transfer roller 9, and the deteriorated toner moved onto the photosensitive drum 5 is transferred onto the transport belt 23 by transfer. Since the deteriorated toner moved onto the transport belt 23 is removed by the belt cleaning blade 29 and stored in the waste toner tank 30, it is prevented that the deteriorated toner is clogged in the waste toner transport path 24.

In order to confirm the effect of the waste toner disposal processing of this example, the following evaluation test was performed.
In the evaluation test, when continuous printing at a printing rate of 42 pages / min and a 0.3% duty was performed on A4 size paper, the waste toner is removed if the deteriorated toner discarding process of this embodiment is performed every time when printing is performed. A test was made as to whether toner clogging occurred in the conveyance path 24 and compared with the printer of Example 1 above. The evaluation results are shown in FIG.

  As shown in FIG. 10, in the printer of the first embodiment, when the printing speed is 42 pages / minute and the deteriorated toner discarding process of the first embodiment is performed for every less than 1000 sheets of A4 size paper, the waste toner transport path 24 is clogged with toner. In this embodiment, even if the deteriorated toner discarding process of this embodiment is performed once every 100 sheets of A4 size paper at a printing speed of 42 pages / minute, the toner is transferred to the waste toner transport path 24. It was found that no clogging occurred.

  Note that the result of the evaluation test on the occurrence of smudge printing when the deteriorated toner discarding process of this example was performed was the same as that of Example 1 above.

  As described above, in this embodiment, deteriorated toner such as highly charged toner and small particle size toner having a significantly increased charge amount is temporarily accumulated in the collecting roller 16 in the printing process, and the accumulated deteriorated toner is In the deteriorated toner disposal step during image formation, the toner is moved from the collection roller 16 to the photosensitive drum 5 via the developing roller 13, and the deteriorated toner moved onto the photosensitive drum 5 is further moved onto the conveying belt 23. Since it is removed by the belt cleaning blade 29 and discarded, it is possible to suppress a decrease in the accumulation efficiency of the deteriorated toner of the collecting roller 16, and as a result, it is possible to prevent the occurrence of printing defects such as smudge printing, and always have a good print quality. Output image can be obtained.

  Further, in the deteriorated toner discarding process of this embodiment, the voltage applied to the supply roller 14 and the developing roller 13 is set to be the same, so that normal toner is prevented from being supplied from the supply roller 14 to the developing roller 13. can do.

  Further, in the deteriorated toner discarding process of the first embodiment, the waste toner conveyance path is used in an extreme environment where the toner tends to solidify such as continuous printing at a high temperature and a high humidity, for example, a temperature of 28 ° C. and a humidity of 80% and 80% duty. In the deteriorated toner discarding process of this embodiment, the deteriorated toner is moved to the transport belt 23, removed by the belt cleaning blade 29, and collected in the waste toner tank 30. Even in such an extreme environment, toner clogging does not occur.

  As described above, in this embodiment, the developing device of the printer is provided with a collecting roller that collects undeveloped toner on the developing roller and accumulates deteriorated toner, and collects it during non-image formation when no image forming operation is performed. The deteriorated toner accumulated in the roller is moved to the developing roller, the deteriorated toner moved to the developing roller is attached to the photosensitive drum, and the deteriorated toner attached to the photosensitive drum is transferred to the conveyance belt by the transfer roller, By removing the deteriorated toner transferred to the conveyor belt with a belt cleaning blade, the deteriorated toner generated in the developing device can be reliably recovered by a recovery roller and automatically discarded when non-image formation is performed. It is possible to prevent the occurrence of smudge printing in high-speed printing, improve the printing quality, and in the waste toner conveyance path. It is possible to prevent the occurrence of clogging toner.

  In each of the above embodiments, the image forming apparatus is described as being a non-magnetic one-component electrophotographic color printer. However, the image forming apparatus is not limited to the above, and an image forming unit using an electrophotographic system is used. Monochrome printers, copiers, etc. having

DESCRIPTION OF SYMBOLS 1 Image formation part 2 Paper 4 Developing apparatus 5 Photosensitive drum 5a, 16a, 27a, 32a Drive motor 6 Charging roller 6b Charging voltage power supply 7 Exposure head 8 Developing apparatus 9 Transfer roller 9b Transfer voltage power supply 10 Drum cleaning blade 11 Static elimination apparatus 13 Developing roller 13b Developing voltage power supply 14 Supply roller 14b Supply voltage power supply 15 Layer regulating blade 15b Layer regulating voltage power supply 16 Collection roller 16b Collection voltage power supply 17 Toner cartridge 18 Toner chamber 20 Collection roller shaft 21 Foam layer 22 Mesh layer 23 Conveying belt 24 Waste toner transport path 25 Waste toner transport spiral 27 Drive roller 28 Driven roller 29 Belt cleaning blade 30 Waste toner tank 31 Fixing device 32 Heating roller 33 Pressure roller 35 Control unit 36 Storage unit 37 During printing Pressure table 38 toner waste when a voltage table

Claims (6)

A latent image carrier;
A developer carrier for developing the latent image on the latent image carrier with a developer;
Developer supplying means for supplying the developer to the developer carrying member;
A developer collecting means for collecting the developer on the developer carrying member and accumulating a deteriorated developer;
A latent image carrier cleaning member that removes the developer remaining on the latent image carrier from the latent image carrier;
At the time of non-image formation in which no image forming operation is performed, the deteriorated developer accumulated in the developer collecting means is moved to the developer carrier,
The deteriorated developer moved to the developer carrier is attached to the latent image carrier,
An image forming apparatus, wherein the deteriorated developer adhered to the latent image carrier is removed by the latent image carrier cleaning member. A latent image carrier;
A developer carrier for developing the latent image on the latent image carrier with a developer;
Developer supplying means for supplying the developer to the developer carrying member;
A developer collecting means for collecting the developer on the developer carrying member and accumulating a deteriorated developer;
Transfer means for transferring the developed latent image on the latent image carrier onto a medium;
Medium conveying means for contacting the latent image carrier and conveying the medium;
A medium conveying means cleaning member for removing the developer remaining on the medium conveying means from the medium conveying means,
At the time of non-image formation in which no image forming operation is performed, the deteriorated developer accumulated in the developer collecting means is moved to the developer carrier,
The deteriorated developer moved to the developer carrier is attached to the latent image carrier,
The deteriorated developer attached to the latent image carrier is transferred to the medium transport unit by the transfer unit,
The image forming apparatus, wherein the deteriorated developer transferred to the medium conveying unit is removed by the medium conveying unit cleaning member. The image forming apparatus according to claim 1, wherein:
The image forming apparatus, wherein the developer collecting unit rotates in a direction opposite to a rotation direction of the developer carrying member during the non-image formation. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the developer collecting unit selectively accumulates a developer having a small particle size from the developer. The image forming apparatus according to claim 4.
The developer collecting means includes a shaft serving as a rotation center, a foam layer that is coated on the outer peripheral surface of the shaft and stores the deteriorated developer, and a mesh layer provided on the outer peripheral surface of the foam layer. An image forming apparatus. The image forming apparatus according to any one of claims 1 to 5,
Voltage application means for applying a voltage to the developer carrier and the developer recovery means,
The voltage application means, during the non-image formation, makes the polarity of the voltage of the developer carrier and the developer recovery means the same as the charging polarity of the developer, and the absolute value of the voltage of the developer carrier Is applied as less than the absolute value of the voltage of the developer recovery means.

Images